Method for accurate fault location in multi-type cable connection system, a device and a storage medium thereof

ABSTRACT

A method for accurate fault location in multi-type cable connection system is provided that includes, first normalizing the measurement parameters, then grouping the data, calculating compensation correction, finding the maximum value of the data, and comparing whether the cable has faults or not. By means of a blended data automatic analysis algorithm of the method, in the presence of multiple cables, data obtained through one-time measurement can be accurately identified to determine data of each scanning point belongs to which cable, and after data allocation is completed, each group of data is separately corrected by using cable parameters corresponding to the group of data, thereby obtaining an accurate fault position and a DTF return loss result.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of China invention Patent ApplicationNo. 201711318131.4 filed Dec. 12, 2017, the contents of which are herebyincorporated by reference.

FIELD OF TECHNOLOGY

The present invention relates to the technical field of fault locationin cable, especially to the technical field of accurate fault locationin multi-type cable connection system, in particular to a method foraccurate fault location by using in multi-type cable connection system,a device and a storage medium thereof.

DESCRIPTION OF RELATED ARTS

The technology of cable fault location is widely used. For example,communication cable may be composed of one cable, or may be composed ofmultiple cables through connectors etc. The connector may be loose or bedamaged in the process of using, and it may result in a decline in theperformance of the entire communication cable, in which case cable faultlocation technology is required for fault location.

The traditional method for cable fault location mainly uses cable andantenna analyzers. The measurement format of the cable and antennaanalyzer is DTF_SWR, and set values of velocity factor of cable, cableloss, value of measured distance and numbers of selected measuringpoints. According to the measurement result of the cable and antennaanalyzer, the location of fault point can be obtained. If the cable runsnormally, the actual length of the cable can be measured. For a singletype of cable, the cable and antenna analyzer can accurately locate thefault point. However, in the actual cable system, many types of cablesmay be used, and each cable is with different parameters. If thetraditional positioning method is used for fault location, the cable andantenna analyzer cannot distribute the scan data according to differentcables. It can only be processed according to one type of cable, so thelocation of fault point will be inaccurate. For example, the maintenanceman locate the leaky cable in the high-speed rail tunnel. If the leakycable system consists of multiple types of cables, there is a largedeviation in the location of location of fault point which is located byusing the traditional method for accurate fault location with cable andantenna analyzers.

Therefore, the current prior art needed to be developed.

SUMMARY OF THE INVENTION

In view of the shortcomings of the above mentioned existing technology,the present invention aims to provide an efficient and accurate methodfor accurate fault location in multi-type cable connection system thatcan effectively solve accurate fault location problem of multi-typecable connection system, of which the operation process is simple andfast, the work performance is stable and reliable, and the scope ofapplication is wide.

Another purpose of the present invention is to provide a device forrealizing accurate fault location in multi-type cable connection system.

Another further purpose of the present invention is to provide acomputer readable storage medium to implement the method for accuratefault location in multi-type cable connection system.

In order to achieve the above purpose, the method, device and computerreadable storage medium for accurate fault location in multi-type cableconnection system of the present invention implements the followingtechnical solutions:

The method for accurate fault location in multi-type cable connectionsystem, wherein, the method has the following steps:

(1) setting initial data and measurement format of a cable and antennaanalyzer, and exporting M measurement data Data[M] of the said cable andantenna analyzer;

(2) dividing the M measurement data into three sets of data, each set ofdata corresponding to one segment of the cable, and respectivelycalculating the number of measuring points M1, M2, M3 of three sets ofdata;

(3) proceeding the three sets of measurement data separately usinglinear compensation;

(4) calculating DTF_SWR data RData[M] based on the compensated data;

(5) calculating location of fault point.

Preferably, the initial data in step (1) including values of velocityfactor of cable, cable loss, value of measured distance L and numbers ofselected measuring points M.

Preferably, the said value of velocity factor of cable is 1.

Preferably, the said cable loss is 0.

Preferably, the said value of measured distance L accords with thefollowing formula:

${L \geq \left( {\frac{L1}{V1} + \frac{L2}{V2} + \frac{L_{x}}{V3}} \right)};$

wherein, L1 is length of the first cable, L2 is length of the secondcable, L_(x) is length of the third cable, V1 is value of velocityfactor of the first segment of the cable, V2 is value of velocity factorof the second segment of the cable, and V3 is value of velocity factorof the third segment of the cable.

Preferably, the process of calculating the number of measuring point M1of one set of data in step (2), is:

calculating the number of measuring point M1 of one set of dataaccording to following formula:

${{M1} = \frac{M \times L\; 1}{\left( {{L1} + {L2} + L_{x}} \right)}};$

wherein, M is the number of selected measurement point, L1 is length ofthe first segment of the cable, L2 is length of the second segment ofthe cable, L_(x) is length of the third segment of the cable.

Preferably, calculating the number of measuring point M2 of one set ofdata in step (2), is:

calculating the number of measuring point M2 of one set of dataaccording to following formula:

${{M2} = \frac{M \times L2}{\left( {{L1} + {L2} + L_{x}} \right)}},;$

wherein, M is the number of selected measurement point, L1 is length ofthe first segment of the cable, L2 is length of the second segment ofthe cable, L_(x) is length of the third segment of the cable.

Preferably, calculating the number of measuring point M3 of one set ofdata in step (2), is:

calculating the number of measuring point M3 of one set of dataaccording to following formula:

M3=M−M1−M2;

wherein, M is the number of selected measurement point.

Preferably, the step in step (3) specifically comprising the followingsteps:

(3.1) calculating the first set of measurement data of the first segmentof the cable with using linear compensation;

(3.2) calculating the second set of measurement data of the secondsegment of the cable with using linear compensation;

(3.3) calculating proceeding the third set of measurement data of thethird segment of the cable with using linear compensation.

Preferably, calculating the first set of measurement data of the firstsegment of the cable with using linear compensation in step (3.1), is:

calculating the first set of measurement data of the first segment ofthe cable with using linear compensation according to following formula:

NData[N]=Data[N]+N×Loss1×2;

wherein, Loss 1 is cable loss of the first segment of the cable, and thevalue of N is 0, 1, . . . , M1−1.

Preferably, calculating the second set of measurement data of the secondsegment of the cable with using linear compensation in step (3.2), is:

calculating the second set of measurement data of the second segment ofthe cable with using linear compensation according to following formula:

CLoss1=L1×Loss1×2;

NData[N]=Data[N]+(N−M1)×Loss2×2+CLoss1;

wherein L1 is length of the first segment of the cable, Loss1 is cableloss of the first segment of the cable, Loss2 is cable loss of thesecond segment of the cable, CLoss1 is fixed loss of the first segmentof the cable, and the value of N is M1, . . . , (M1+M2−1).

Preferably, calculating the third set of measurement data of the thirdsegment of the cable with using linear compensation in step (3.3), is:

calculating the third set of measurement data of the third segment ofthe cable with using linear compensation according to following formula:

CLoss2=L2×Loss2×2;

NData[N]=Data[N]+(N−M1−M2)×Loss3×2+CLoss1+CLoss2;

wherein, L2 is length of the second segment of the cable, Loss2 is cableloss of the second segment of the cable, Loss3 is cable loss of thethird segment of the cable, CLoss1 is fixed loss of the first segment ofthe cable, CLoss2 is fixed loss of the second segment of the cable, andthe value of N is (M1+M2), . . . , (M−1).

Preferably, calculating DTF_SWR data RData[M] in step (4), is:

calculating DTF_SWR data RData[M] according to following formula:

${{Rho} = 10^{\frac{{- N}Dat{a{\lbrack N\rbrack}}}{2}}};$${{RData}\lbrack N\rbrack} = \left\{ {\begin{matrix}{1000\left( {{Rho} = 1} \right)} \\{{{1 + {Rho}}}\left( {{Rho} \neq 1} \right)}\end{matrix};} \right.$

wherein, Rho is reflection coefficient, NData[N] is compensation valueof measurement data.

Preferably, the step in step (5) further including the following steps:

(5.1) searching RData[N], and recording maximum value RMax in RData[N]and its corresponding position I in RData[N];

(5.2) judging whether the maximum value RMax is greater than presetthreshold SWR_Limit of DTF_SWR or not; and if so, the cable system is introuble, then calculating and recording the fault point positionDTF_Len; otherwise, the cable system runs normally.

Preferably, calculating the fault point position DTF_Len in step (5.2),is:

calculating the fault point position DTF_Len according to followingformula:

${{DFT}_{Len} = {I \times \frac{\left( {{L1} + {L2} + L_{x}} \right)}{M - 1}}};$

wherein, L1 is length of the first segment of the cable, L2 is length ofthe second segment of the cable, L_(x) is length of the third segment ofthe cable.

The said device for realizing accurate fault location in multi-typecable connection system, wherein, the device comprising a storage forstoring programs and a processor for executing the said programs, whichimplements the above method for accurate fault location in multi-typecable connection system.

The said computer readable storage medium, wherein storing program, theprogram is executed by processor to implement the above method foraccurate fault location in multi-type cable connection system.

The beneficial effect of the present invention compared with theexisting technology is: through the hybrid data automatic analysisalgorithm of the present invention, the data obtained from onemeasurement can be accurately identified as the data of each scanningpoint belongs to which segment of the cables. Each set of data can becorrected with the cable parameters corresponding to the set of datarespectively after the data distribution, so that the accurate locationsof fault point and the results of DTF Return Loss are obtained. By usingthe new method of fault location, the accuracy of cable positionmeasurement is greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall flow chart of the method for accurate faultlocation in multi-type cable connection system.

FIG. 2 is the measurement result diagram by using traditional measuringmethods to measure cables.

FIG. 3 is the cable measurement result diagram of the examples of themethod for accurate fault location in multi-type cable connection systemin the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is further exemplified hereinafter by reference tothe accompanying drawings and the following embodiments to make theobject, technical solutions and advantages of the present invention moreclear. It is understood that the specific embodiments in thisapplication is only used to explain the present invention instead oflimit the present invention.

It should be noted that when a component is referred to as being “fixed”or “set” another component, it can be directly on another component orpossibly exist a centralized component at the same time. When acomponent is referred to as being “connected” to another component, itcan be directly connected to another component or may exist acentralized component at the same time.

It should also be noted that the expressions of left, right, upper andlower directions in the embodiments of the present invention are merelyrelative concepts or refer to the normal usage state of the productinstead of be limited.

The method for accurate fault location in multi-type cable connectionsystem in this invention, wherein the method has the following steps:

(1) setting initial data and measurement format of a cable and antennaanalyzer, and exporting M measurement data Data[M] of the said cable andantenna analyzer;

(2) dividing the M measurement data into three sets of data, each set ofdata corresponding to one segment of the cable, and respectivelycalculating the number of measuring points M1, M2, M3 of three sets ofdata;

(3) proceeding the three sets of measurement data separately usinglinear compensation;

(3.1) calculating the first set of measurement data of the first segmentof the cable with using linear compensation;

(3.2) calculating the second set of measurement data of the secondsegment of the cable with using linear compensation;

(3.3) calculating proceeding the third set of measurement data of thethird segment of the cable with using linear compensation;

(4) calculating DTF_SWR data RData[M] based on the compensated data;

(5) calculating location of fault point;

(5.1) searching RData[N], and recording maximum value RMax in RData[N]and its corresponding position I in RData[N];

(5.2) judging whether the maximum value RMax is greater than presetthreshold SWR_Limit of DTF_SWR or not; and if so, the cable system is introuble, then calculating and recording the fault point positionDTF_Len; otherwise, the cable system runs normally.

As a preferred embodiment of the present invention, the initial data instep (1) including values of velocity factor of cable, cable loss, valueof measured distance L and numbers of selected measuring points M.

As a preferred embodiment of the present invention, the said value ofvelocity factor of cable is 1.

As a preferred embodiment of the present invention, the said cable lossis 0.

As a preferred embodiment of the present invention, the said value ofmeasured distance L accords with the following formula:

${L \geq \left( {\frac{L1}{V1} + \frac{L2}{V2} + \frac{L_{x}}{V3}} \right)};$

wherein, L1 is length of the first cable, L2 is length of the secondcable, L_(x) is length of the third cable, V1 is value of velocityfactor of the first segment of the cable, V2 is value of velocity factorof the second segment of the cable, and V3 is value of velocity factorof the third segment of the cable.

As a preferred embodiment of the present invention, the process ofcalculating the number of measuring point M1 of one set of data in step(2), is:

calculating the number of measuring point M1 of one set of dataaccording to following formula:

${{M1} = \frac{M \times L1}{\left( {{L1} + {L2} + L_{x}} \right)}};$

wherein, M is the number of selected measurement point, L1 is length ofthe first segment of the cable, L2 is length of the second segment ofthe cable, L_(x) is length of the third segment of the cable.

As a preferred embodiment of the present invention, calculating thenumber of measuring point M2 of one set of data in step (2), is:

calculating the number of measuring point M2 of one set of dataaccording to following formula:

${{M2} = \frac{M \times L2}{\left( {{L1} + {L2} + L_{x}} \right)}};$

wherein, M is the number of selected measurement point, L1 is length ofthe first segment of the cable, L2 is length of the second segment ofthe cable, L_(x) is length of the third segment of the cable.

As a preferred embodiment of the present invention, calculating thenumber of measuring point M3 of one set of data in step (2), is:

calculating the number of measuring point M3 of one set of dataaccording to following formula:

M3=M−M1−M2;

wherein, M is the number of selected measurement point.

As a preferred embodiment of the present invention, calculating thefirst set of measurement data of the first segment of the cable withusing linear compensation in step (3.1), is:

calculating the first set of measurement data of the first segment ofthe cable with using linear compensation according to following formula:

NData[N]=Data[N]+N×Loss1×2;

wherein, Loss1 is cable loss of the first segment of the cable, and thevalue of N is 0, 1, . . . , M1−1.

As a preferred embodiment of the present invention, calculating thesecond set of measurement data of the second segment of the cable withusing linear compensation in step (3.2), is:

calculating the second set of measurement data of the second segment ofthe cable with using linear compensation according to following formula:

CLoss1=L1×Loss1×2;

NData[N]=Data[N]+(N−M1)×Loss2×2+CLoss1;

wherein, L1 is length of the first segment of the cable, Loss1 is cableloss of the first segment of the cable, Loss2 is cable loss of thesecond segment of the cable, CLoss1 is fixed loss of the first segmentof the cable, and the value of N is M1, . . . , (M1+M2−1).

As a preferred embodiment of the present invention, calculating thethird set of measurement data of the third segment of the cable withusing linear compensation in step (3.3), is:

calculating the third set of measurement data of the third segment ofthe cable with using linear compensation according to following formula:

CLoss2=L2×Loss2×2;

NData[N]=Data[N]+(N−M1−M2)×Loss3×2+CLoss1+CLoss2;

wherein, L2 is length of the second segment of the cable, Loss2 is cableloss of the second segment of the cable, Loss3 is cable loss of thethird segment of the cable, CLoss1 is fixed loss of the first segment ofthe cable, CLoss2 is fixed loss of the second segment of the cable, andthe value of N is (M1+M2), . . . , (M−1).

As a preferred embodiment of the present invention, calculating DTF_SWRdata RData[M] in step (4), is:

calculating DTF_SWR data RData[M] according to following formula:

${{Rho} = 10^{\frac{{- N}Dat{a{\lbrack N\rbrack}}}{2}}};$${{RData}\lbrack N\rbrack} = \left\{ {\begin{matrix}{1000\left( {{Rho} = 1} \right)} \\{{{1 + {Rho}}}\left( {{Rho} \neq 1} \right)}\end{matrix};} \right.$

wherein, Rho is reflection coefficient, NData[N] is compensation valueof measurement data.

As a preferred embodiment of the present invention, calculating thefault point position DTF_Len in step (5.2), is:

calculating the fault point position DTF_Len according to followingformula:

${{DFT}_{Len} = {I \times \frac{\left( {{L\; 1} + {L\; 2} + L_{x}} \right)}{M - 1}}},$

wherein, L1 is length of the first segment of the cable, L2 is length ofthe second segment of the cable, L_(x) is length of the third segment ofthe cable.

In practice, as shown in FIG. 1, it is an overall flow chart of themethod for accurate fault location in multi-type cable connectionsystem.

Where the method includes the following steps:

step S1: selecting the measurement format of the cable and antennaanalyzer as DTF_Return_Loss, and setting the value of velocity factor ofthe cable to 1, the cable loss to 0, the value of measured distance toL, and selecting the number of measurement points as M, wherein L shouldbe satisfied the formula (1):

$L \geq \left( {\frac{L\; 1}{V\; 1} + \frac{L\; 2}{V\; 2} + \frac{Lx}{V\; 3}} \right)$

step S2: exporting M measurement data Data[M] of the cable and antennaanalyzer;

step S3: dividing M measurement data into three sets of data, each setof data corresponding to one segment of the cable, and the points ofthree sets of data are M1 (formula (2)), M2 (formula (3)) and M3(formula (4)):

$\begin{matrix}{{M1} = \frac{M \times L1}{\left( {{L1} + {L2} + {Lx}} \right)}} & (2) \\{{M\; 2} = \frac{M \times L\; 2}{\left( {{L\; 1} + {L\; 2} + {Lx}} \right)}} & (3) \\{{M\; 3} = {M - {M\; 1} - {M\; 2}}} & (4)\end{matrix}$

step S4: proceeding measurement data separately by using linearcompensation;

step S401: calculating the first set of measurement data of the firstsegment of the cable with using linear compensation, according toformula (5):

NData[N]=Data[N]+N×Loss1×2   (5)

wherein, the value of N is 0, 1, . . . , M1−1.

step S402: calculating the second set of measurement data of the secondsegment of the cable with using linear compensation, according toformula (6):

CLoss1=L1×Loss1×2

NData[N]=Data[N]+(N−M1)×Loss2×2+CLoss1   (6)

wherein the value of N is M1, . . . , (M1+M2−1), and CLoss1 is fixedloss of the first segment of the cable.

step S403: calculating proceeding the third set of measurement data ofthe third segment of the cable with using linear compensation, accordingto formula (7):

CLoss2=L2×Loss2×2

NData[N]=Data[N]+(N−M1−M2)×Loss3*2+CLoss1+CLoss2   (7)

wherein the value of N is (M1+M2), . . . , (M−1), and CLoss2 is fixedloss of the second segment of the cable.

step S5: calculating DTF_SWR data according to NData[M] data, and besaved as RData[M] by using formula (8):

$\begin{matrix}{{{Rho} = 10^{\frac{- {{NData}{\lbrack N\rbrack}}}{2}}}{{{RData}\lbrack N\rbrack} = \left\{ \begin{matrix}{1000\left( {{Rho} = 1} \right)} \\{{{1 + {Rho}}}\left( {{Rho} \neq 1} \right)}\end{matrix} \right.}} & (8)\end{matrix}$

step S6: calculating location of fault point.

Wherein the concrete linear compensation in step S4 includes thefollowing steps:

Specifically, calculating the fault location in step S6 includes thefollowing steps:

step S601: searching RData[N], and recording maximum value in RData[N]as RMax, recording its corresponding position in RData[N] as I;

step S602: comparing RMax to preset threshold SWR_Limit of DTF_SWR; ifthe value of RMax is bigger than the value of SWR_Limit, and so thecable system is in trouble, recording the fault point position asDTF_Len, wherein DTF_Len should be satisfied the formula (9):

$\begin{matrix}{{DTF\_ Len} = {I \times \frac{\left( {{L1} + {L2} + {Lx}} \right)}{M - 1}}} & (9)\end{matrix}$

If the value of RMax is smaller than the value of SWR_Limit, then thecable system runs normally.

Specifically, the lengths of the first segment cable and the secondsegment cable are accurate lengths, that is to say, L1 and L2 aredetermined lengths, and the length of the third segment cable Lx may bea determined length or an estimated length.

Wherein, the position corresponding to RMax in RData[N] is recorded as Iin step S601, which is be calculated as 0 from beginning.

In the specific experiment, the actual length of each cable is L1=92 m,L2=106 m, L3=200 m, and the actual total length is 398 m.

FIG. 2 shows the results of measuring the cable system by using thetraditional test method. The total length of three cables is 377.1 mwith an error of 20.9 m.

FIG. 3 shows the results of measuring the cable system by using abovemethod in the present invention, and the result is 398.15 m with anerror of 0.15 m.

It can be seen from the comparison of the experimental results that themethod of the present invention is indeed superior to the conventionalpositioning method, and is capable of accurately locating the faultlocation.

Meanwhile, the device for realizing accurate fault location inmulti-type cable connection system in the present invention, whereincomprising a storage for storing programs and a processor for executingthe said programs, which implements above method for accurate faultlocation in multi-type cable connection system.

The said computer readable storage medium, wherein storing program, theprogram is executed by processor to implement the said method foraccurate fault location in multi-type cable connection system.

By means of a blended data automatic analysis algorithm in the presentinvention, in the presence of multiple cables, data obtained throughone-time measurement can be accurately identified to determine data ofeach scanning point belongs to which cable, and after data allocation iscompleted, each group of data is separately corrected by using cableparameters corresponding to the group of data, thereby obtaining anaccurate fault position and a DTF return loss result. Through this newmethod of fault location, the accuracy of cable position measurement isgreatly improved.

The above is only a preferred embodiment of the present invention, andis not intended to limit the present invention. Any modifications,equivalent substitutions and improvements made within the spirit andprinciples of the present invention should be included in the scope ofprotection of the present invention. Meanwhile, The present inventionhas been described with reference to the specific embodiments, and it isobvious that various modifications and changes can be made withoutdeparting from the spirit and scope of protection of the invention.Therefore, the instructions and drawings should be consideredillustrative rather than restrictive.

1. A method for accurate fault location in multi-type cable connectionsystem, characterized in that, the method comprising: (1) settinginitial data and measurement format of a cable and antenna analyzer, andexporting M measurement data Data[M] of the said cable and antennaanalyzer; (2) dividing the M measurement data into three sets of data,each set of data corresponding to one segment of the cable, andrespectively calculating the number of measuring points M1, M2, M3 ofthree sets of data; (3) proceeding the three sets of measurement dataseparately using linear compensation; (4) calculating DTF_SWR dataRData[M] based on the compensated data; and (5) calculating location offault point.
 2. The method for accurate fault location in multi-typecable connection system according to claim 1, characterized in that, theinitial data in step (1) including values of velocity factor of cable,cable loss, value of measured distance L and numbers of selectedmeasuring points M.
 3. The method for accurate fault location inmulti-type cable connection system according to claim 2, characterizedin that, the said value of velocity factor of cable is
 1. 4. The methodfor accurate fault location in multi-type cable connection systemaccording to claim 2, characterized in that, the said cable loss is 0.5. The method for accurate fault location in multi-type cable connectionsystem according to claim 2, characterized in that, the said value ofmeasured distance L accords with the following formula:${L \geq \left( {\frac{L\; 1}{V\; 1} + \frac{L\; 2}{V\; 2} + \frac{L_{x}}{V\; 3}} \right)};$wherein, L 1 is length of the first cable, L2 is length of the secondcable, L_(x) is length of the third cable, V1 is value of velocityfactor of the first segment of the cable, V2 is value of velocity factorof the second segment of the cable, and V3 is value of velocity factorof the third segment of the cable.
 6. The method for accurate faultlocation in multi-type cable connection system according to claim 1,characterized in that, the process of calculating the number ofmeasuring point M1 of one set of data in step (2), is: calculating thenumber of measuring point M1 of one set of data according to followingformula:${{M\; 1} = \frac{M \times L1}{\left( {{L\; 1} + {L\; 2} + L_{x}} \right)}};$wherein, M is the number of selected measurement point, L1 is length ofthe first segment of the cable, L2 is length of the second segment ofthe cable, L_(x) is length of the third segment of the cable.
 7. Themethod for accurate fault location in multi-type cable connection systemaccording to claim 1, characterized in that, calculating the number ofmeasuring point M2 of one set of data in step (2), is: calculating thenumber of measuring point M2 of one set of data according to followingformula:${{M\; 2} = \frac{M \times L\; 2}{\left( {{L\; 1} + {L\; 2} + L_{x}} \right)}};$wherein, M is the number of selected measurement point, L1 is length ofthe first segment of the cable, L2 is length of the second segment ofthe cable, L_(x) is length of the third segment of the cable.
 8. Themethod for accurate fault location in multi-type cable connection systemaccording to claim 1, characterized in that, calculating the number ofmeasuring point M3 of one set of data in step (2), is: calculating thenumber of measuring point M3 of one set of data according to followingformula:M3=M−M1−M2; wherein, M is the number of selected measurement point. 9.The method for accurate fault location in multi-type cable connectionsystem according to claim 1, characterized in that, the step in step (3)specifically comprising the following steps: (3.1) calculating the firstset of measurement data of the first segment of the cable with usinglinear compensation; (3.2) calculating the second set of measurementdata of the second segment of the cable with using linear compensation;(3.3) calculating proceeding the third set of measurement data of thethird segment of the cable with using linear compensation.
 10. Themethod for accurate fault location in multi-type cable connection systemaccording to claim 9, characterized in that, calculating the first setof measurement data of the first segment of the cable with using linearcompensation in step (3.1), is: calculating the first set of measurementdata of the first segment of the cable with using linear compensationaccording to following formula:NData[N]=Data[N]+N×Loss1×2; wherein, Loss1 is cable loss of the firstsegment of the cable, and the value of N is 0, 1, . . . , M1−1.
 11. Themethod for accurate fault location in multi-type cable connection systemaccording to claim 9, characterized in that, calculating the second setof measurement data of the second segment of the cable with using linearcompensation in step (3.2), is: calculating the second set ofmeasurement data of the second segment of the cable with using linearcompensation according to following formula:CLoss1=L1×Loss1×2;NData[N]=Data[N]+(N−M1)×Loss2×2+CLoss1; wherein, L1 is length of thefirst segment of the cable, Loss1 is cable loss of the first segment ofthe cable, Loss2 is cable loss of the second segment of the cable,CLoss1 is fixed loss of the first segment of the cable, and the value ofN is M1, . . . , (M1+M2−1).
 12. The method for accurate fault locationin multi-type cable connection system according to claim 9,characterized in that, calculating the third set of measurement data ofthe third segment of the cable with using linear compensation in step(3.3), is: calculating the third set of measurement data of the thirdsegment of the cable with using linear compensation according tofollowing formula:CLoss2=L2×Loss2×2;NData[N]=Data[N]+(N−M1−M2)×Loss3×2+CLoss1+CLoss2; wherein, L2 is lengthof the second segment of the cable, Loss2 is cable loss of the secondsegment of the cable, Loss3 is cable loss of the third segment of thecable, CLoss1 is fixed loss of the first segment of the cable, CLoss2 isfixed loss of the second segment of the cable, and the value of N is(M1+M2), . . . , (M−1).
 13. The method for accurate fault location inmulti-type cable connection system according to claim 9, characterizedin that, calculating DTF_SWR data RData[M] in step (4), is: calculatingDTF_SWR data RData[M] according to following formula:${{Rho} = 10^{\frac{- {{NData}{\lbrack N\rbrack}}}{2}}};$${{RData}\lbrack N\rbrack} = \left\{ {\begin{matrix}{1000\left( {{Rho} = 1} \right)} \\{{{1 + {Rho}}}\left( {{Rho} \neq 1} \right)}\end{matrix};} \right.$ wherein, Rho is reflection coefficient, NData[N]is compensation value of measurement data.
 14. The method for accuratefault location in multi-type cable connection system according to claim1, characterized in that, the step in step (5) further including thefollowing steps: (5.1) searching RData[N], and recording maximum valueRMax in RData[N] and its corresponding position I in RData[N]; (5.2)judging whether the maximum value RMax is greater than preset thresholdSWR_Limit of DTF_SWR or not; and if so, the cable system is in trouble,then calculating and recording the fault point position DTF_Len;otherwise, the cable system runs normally.
 15. The method for accuratefault location in multi-type cable connection system according to claim14, characterized in that, calculating the fault point position DTF_Lenin step (5.2), is: calculating the fault point position DTF_Lenaccording to following formula:${{DTF}_{Len} = {I \times \frac{\left( {{L1} + {L2} + L_{x}} \right)}{M - 1}}};$wherein, L1 is length of the first segment of the cable, L2 is length ofthe second segment of the cable, L_(x) is length of the third segment ofthe cable.
 16. A device for realizing accurate fault location inmulti-type cable connection system, characterized in that, comprising astorage for storing programs and a processor for executing the saidprograms, which implements the said method for accurate fault locationin multi-type cable connection system of claim
 1. 17. A computerreadable storage medium, characterized in that, storing program, theprogram is executed by processor to implement the said method foraccurate fault location in multi-type cable connection system claim 1.18. The device for realizing accurate fault location in multi-type cableconnection system according to claim 16, characterized in that, theinitial data in step (1) including values of velocity factor of cable,cable loss, value of measured distance L and numbers of selectedmeasuring points M; the said value of velocity factor of cable is 1, thesaid cable loss is 0, the said value of measured distance L accords withthe following formula:${L \geq \left( {\frac{L\; 1}{V\; 1} + \frac{L\; 2}{V\; 2} + \frac{L_{x}}{V\; 3}} \right)};$wherein, L1 is length of the first cable, L2 is length of the secondcable, L_(x) is length of the third cable, V1 is value of velocityfactor of the first segment of the cable, V2 is value of velocity factorof the second segment of the cable, and V3 is value of velocity factorof the third segment of the cable.
 19. The device for realizing accuratefault location in multi-type cable connection system according to claim16, characterized in that, the process of calculating the number ofmeasuring point M1 of one set of data in step (2), is: calculating thenumber of measuring point M1 of one set of data according to followingformula:${{M\; 1} = \frac{M \times L1}{\left( {{L\; 1} + {L\; 2} + L_{x}} \right)}};$wherein, M is the number of selected measurement point, L1 is length ofthe first segment of the cable, L2 is length of the second segment ofthe cable, L_(x) is length of the third segment of the cable;calculating the number of measuring point M2 of one set of data in step(2), is: calculating the number of measuring point M2 of one set of dataaccording to following formula:${{M\; 2} = \frac{M \times L\; 2}{\left( {{L\; 1} + {L\; 2} + L_{x}} \right)}};$wherein, M is the number of selected measurement point, L1 is length ofthe first segment of the cable, L2 is length of the second segment ofthe cable, L_(x) is length of the third segment of the cable;calculating the number of measuring point M3 of one set of data in step(2), is: calculating the number of measuring point M3 of one set of dataaccording to following formula:M3=M−M1−M2; wherein, M is the number of selected measurement point. 20.The device for realizing accurate fault location in multi-type cableconnection system according to claim 16, characterized in that, the stepin step (3) specifically comprising the following steps: (3.1)calculating the first set of measurement data of the first segment ofthe cable with using linear compensation; is: calculating the first setof measurement data of the first segment of the cable with using linearcompensation according to following formula:NData[N]=Data[N]+N×Loss1×2; wherein, Loss1 is cable loss of the firstsegment of the cable, and the value of N is 0, 1, . . . , M1−1; (3.2)calculating the second set of measurement data of the second segment ofthe cable with using linear compensation; is: calculating the second setof measurement data of the second segment of the cable with using linearcompensation according to following formula:CLoss1=L1×Loss1×2;NData[N]=Data[N]+(N−M1)×Loss2×2+CLoss1; wherein, L1 is length of thefirst segment of the cable, Loss 1 is cable loss of the first segment ofthe cable, Loss2 is cable loss of the second segment of the cable,CLoss1 is fixed loss of the first segment of the cable, and the value ofN is M1, . . . , (M1+M2−1); (3.3) calculating proceeding the third setof measurement data of the third segment of the cable with using linearcompensation; is: calculating the third set of measurement data of thethird segment of the cable with using linear compensation according tofollowing formula:CLoss2=L2×Loss2×2;NData[N]=Data[N]+(N−M1−M2)×Loss3×2+CLoss1+CLoss2; wherein, L2 is lengthof the second segment of the cable, Loss2 is cable loss of the secondsegment of the cable, Loss3 is cable loss of the third segment of thecable, CLoss1 is fixed loss of the first segment of the cable, CLoss2 isfixed loss of the second segment of the cable, and the value of N is(M1+M2), . . . , (M−1); calculating DTF_SWR data RData[M] in step (4),is: calculating DTF_SWR data RData[M] according to following formula:${{Rho} = 10^{\frac{- {{NData}{\lbrack N\rbrack}}}{2}}};$${{RData}\lbrack N\rbrack} = \left\{ {\begin{matrix}{1000\left( {{Rho} = 1} \right)} \\{{{1 + {Rho}}}\left( {{Rho} \neq 1} \right)}\end{matrix};} \right.$ wherein, Rho is reflection coefficient, NData[N]is compensation value of measurement data.
 21. The device for realizingaccurate fault location in multi-type cable connection system accordingto claim 16, characterized in that, the step in step (5) furtherincluding the following steps: (5.1) searching RData[N], and recordingmaximum value RMax in RData[N] and its corresponding position I inRData[N]; (5.2) judging whether the maximum value RMax is greater thanpreset threshold SWR_Limit of DTF_SWR or not; and if so, the cablesystem is in trouble, then calculating and recording the fault pointposition DTF_Len; otherwise, the cable system runs normally; whereincalculating the fault point position DTF_Len in step (5.2), is:calculating the fault point position DTF_Len according to followingformula:${{DTF}_{Len} = {I \times \frac{\left( {{L1} + {L2} + L_{x}} \right)}{M - 1}}};$wherein, L1 is length of the first segment of the cable, L2 is length ofthe second segment of the cable, L_(x) is length of the third segment ofthe cable.